1. Field of the Invention
The present invention relates to a structure of a rear portion of a vehicle furnished with a curtain airbag apparatus.
2. Description of the Related Art
It is now common practice to furnish vehicles, in particular motor vehicles, with an airbag system to provide protection to vehicle occupants in the event of a collision or a rollover, for instance. A so-called “curtain airbag,” a type of currently available airbags, is designed to inflate and deploy in the vehicle interior to cover side window glass panes. Among curtain airbags of different designs, one has a large length so as to be deployed longitudinally to cover a plurality of side window glass panes which are located separately along a longitudinal direction of a vehicle. For example, Japanese Unexamined Patent Publication No. 2004-189099 discloses this type of curtain airbag which has a considerably large longitudinal dimension to cover all three side window glass panes mounted on each side of a vehicle. When in a retracted state, the curtain airbag of this Publication is fixed to a vehicle body along upper marginal parts of the side window glass panes as well as to a rearmost pillar.
On the other hand, United States Patent Publication No. 2004/0150198 introduces a curtain airbag deployment technique in which a curtain airbag is deployed out from a rear pillar trim with an outside edge portion thereof deformed.
Further, Japanese Unexamined Patent Publication No. 2004-314655 shows a structure in which a trim made of a hard material is provided in the vicinity of an upper edge of side window glass. This Publication does not disclose an arrangement for deploying a curtain airbag from a rear pillar trim, however.
It is desirable that a curtain airbag deployed to cover side window glass from inside a vehicle's passenger compartment, especially in the event of a rollover, exhibit a sufficiently high resistance (or unimpaired tensile force) to withstand an external force which may be exerted on the curtain airbag from inside or outside the vehicle interior. For this reason, the curtain airbag should preferably be fixed to the vehicle body not only at an upper portion but also at a rear end portion which is a portion of the curtain airbag disposed along a rear end part of the side window glass.
A rear pillar is covered by a rear pillar trim to provide an improved appearance as seen from inside the passenger compartment, for instance. The rear pillar trim is generally made of material which is much harder than a soft roof trim covering an inner surface of a roof panel so that the rear pillar trim would not be damaged by cargo or other objects. In a case where the curtain airbag is designed to cover a side window glass pane located immediately in front of the rear pillar which is covered by the rear pillar trim, the portion of the curtain airbag disposed along the rear end part of the side window glass is covered by the rear pillar trim in a retracted state so that the same portion of the curtain airbag is seen from inside the passenger compartment. Since the curtain airbag thus designed is covered by the rear pillar trim from a front side in the retracted state, it is needed, when necessary, to deploy the curtain airbag while causing at least an upper part of a frontal portion of the rear pillar trim to deform frontward.
Since the rear pillar trim is made of a hard material as mentioned above, the rear pillar trim is not so easy to deform. Thus, under conditions where the curtain airbag in the retracted state is positioned considerably inward along a width direction of the vehicle, however, it is necessary to deform the rear pillar trim by an extremely large amount when deploying the curtain airbag. This makes it difficult to ensure smooth inflation and deployment of the curtain airbag, potentially causing a breakage of the upper part of the rear pillar trim.
One approach to securing good deployability of the curtain airbag would be to cause the curtain airbag to stretch out from between an outermost end part of the frontal portion of the rear pillar trim and the side window glass when activated. This will be achieved by storing the curtain airbag situated along the rear end part of the side window glass in the retracted state at a position greatly offset outward along the vehicle width (or at a position as close as possible to the side window glass), or by storing the curtain airbag in such a way that the curtain airbag being deployed is directed somewhat outward along the vehicle width. This approach however is likely to develop a problem that the rear pillar trim becomes susceptible to breakage because the curtain airbag being deployed produces a pushing force which exerts a great locally deforming effect on the outermost end part of the rear pillar trim.